Murray Cameron and a team of interviewers spoke to 350 retired RUC officers, including two chief constables, as part of an archiving project launched after the Patten report which reformed policing. But it was not focused on the Troubles as envisaged by the new arrangements.

One former officer told him: " At 2.30 in the afternoon I said goodbye to a couple of cops I was working with. At five they were both dead. I don't want to go back to that."

Mr Cameron added: "Asking people to go into traumatic incidents if they have not dealt with that themselves will re-traumatise. People have enough wit to see that and are constrained from getting into that."

Other victims apart from police also face similar challenges when asked to talk about past violence, the archive's project manager added.

The RUC George Cross Foundation Oral History Project was established by former chief constable Sir Ronnie Flanagan and received Heritage Lottery funding.

Mr Cameron's background is as a civil servant and he said impartiality was important.

"It had to be seen and be able to be demonstrated that there was not an agenda."

They were not "Jeremy Paxman-style" confrontational interviews, he said.

"We decided that we would set people up, put the microphone in front of them and let them say what they wanted to say."

Where people needed help they were directed appropriately but interviewers were trained not to try to intervene and inadvertently make the situation worse.

Each interview lasted about 40 minutes and the entire archive takes about a week and half to listen to.

All ranks contributed, as well as families of officers.

The force at one stage had 12,000 members.

Mr Cameron added: "All we have is a very small proportion of people who served. It was not seen at that time in any way as a recording of facts in relation to incidents."

The interviews have been transcribed and the archive is searchable.

He said much of it was relatively mundane, social history rather than focused on bombs and bullets.

Mr Cameron spoke at a Belfast seminar organised by the Stories Network, which gathers information about the conflict.